sqlite3_open_v2 broken (Unity3D)

[MeikelLP]

I'm using Microsoft.Data.Sqlite to access a sqlite3 file from my Unity3D game.

so I tried like:

using (var conn = new SqliteConnection($"Data Source=Assets\\Data\\database.bwxsdb"))
{
    conn.Open();
}

and I get:

NullReferenceException: Object reference not set to an instance of an object
SQLitePCL.raw.sqlite3_open_v2 (SQLitePCL.utf8z filename, SQLitePCL.sqlite3& db, System.Int32 flags, SQLitePCL.utf8z vfs) (at <15ecb38d58394d7b88b3f841a7dda078>:0)
SQLitePCL.raw.sqlite3_open_v2 (System.String filename, SQLitePCL.sqlite3& db, System.Int32 flags, System.String vfs) (at <15ecb38d58394d7b88b3f841a7dda078>:0)
Microsoft.Data.Sqlite.SqliteConnection.Open () (at <9ffe4c48f3134a7b905b5da527410f26>:0)

I tried this:

var fromString = utf8z.FromString("Assets\\Data\\database.bwxsdb");
var utf8Z = utf8z.FromString(null);
raw.sqlite3_open_v2(fromString, out var db, 0, utf8Z);

and get the same error.

Any reasons why that is not working? The db file is not broken. I can read & write to it via DataGrip.

[MeikelLP]

Apparently I forgot to add required libraries. As we are in the Unity world and cannot use tools like NuGet I have to add the libraries all by myself. So what I need to work with in Unity are:

• Microsoft.Data.Sqlite.dll
• SQLitePCLRaw.batteries_v2.dll
• SQLitePCLRaw.core.dll
• SQLitePCLRaw.provider.e_sqlite3.dll
• System.Buffers.dll
• System.Memory.dll
• System.Runtime.CompilerServices.Unsafe.dll

... and native libraries depending on your platform from the SQLitePCLRaw.lib.e_sqlite3 NuGet package.

Is there a better way to do this?

[bricelam]

v1 used to provide a better exception message:

You need to call SQLitePCL.raw.SetProvider(). If you are using a bundle package, this is done by calling SQLitePCL.Batteries.Init().

[bricelam]

@MeikelLP Have you seen NuGetForUnity? I'm not sure if it supports everything you need to install SQLitePCLRaw, but it's worth a shot.

[MeikelLP]

@bricelam Yes I've seen this but I prefer OpenUPM. But there is no package yet available.

[MeikelLP]

Today I noticed this error again. Not in Unity but rather in ASP.NET Core 3.1.3.
This issue occurs in a console app which I use to wrap my ef migrations add and ef database update without booting up my actual asp net app all the time. Very basic but works fine:

public class Program
{
    public static void Main(string[] args)
        => CreateHostBuilder(args).Build().Run();

    public static IHostBuilder CreateHostBuilder(string[] args)
    {
        return Host.CreateDefaultBuilder(args)
            .ConfigureServices(x => x.AddDbContext<NucleusDbContext>(options =>
            {
                var configuration = x.BuildServiceProvider().GetRequiredService<IConfiguration>();
                options.UseSqlite(configuration.GetConnectionString("DefaultConnection"));
            }));
    }
}

The problem is that I get the exact same error as I got before with Unity:

PS F:\projekte\none\MyCoolProject\Backend\Core> dotnet ef database update --startup-project ..\Migrator\
Build started...
Build succeeded.
info: Microsoft.EntityFrameworkCore.Infrastructure[10403]
      Entity Framework Core 3.1.3 initialized 'NucleusDbContext' using provider 'Microsoft.EntityFrameworkCore.Sqlite' with options: using lazy-loading proxies
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.Data.Sqlite.SqliteConnection.Open()
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnection(Boolean errorsExpected)
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.Open(Boolean errorsExpected)
   at Microsoft.EntityFrameworkCore.Sqlite.Storage.Internal.SqliteDatabaseCreator.Exists()
   at Microsoft.EntityFrameworkCore.Migrations.HistoryRepository.Exists()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabaseImpl(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Object reference not set to an instance of an object.

This can be easily fixed with adding the package reference to that migrator project as well:

<PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="3.1.3" />